In the industry of members for push button switches used in control panels of electronic devices, particularly those of cellular phones, the diversifications for the design and function has further increased. In recent years, as a member for a push button switch used in the electronic device such as a cellular phone, a member having a metallic appearance is used as a high-end design. The member for a push button switch having a metallic appearance has the structure in which a plated layer, a resin molded portion, and a base rubber are layered in the stated order from the push button surface side. The plated layer is, for example, nickel-plated, copper-plated, or chrome-plated (for example, see Patent Document 1). Further, in order to protect the plated layer, a technology of forming a transparent resin coated layer on a surface of the plated layer is known. Also, there is known a member for a push button switch, in which a resin film subjected to metal evaporation is processed by drawing, and the interior thereof is filled with a core material formed of a resin or a rubber with the resin film being used as a outer layer to be integrated.
In order to further increase an upscale impression of electronic devices such as cellular phones, there is also known a member for a push button switch having a structure where a metal push button is attached to a surface of a flexible sheet such as a silicone rubber (for example, see Patent Document 2). Besides, considering the use in a dark place or designability, in this member for a push button switch, a hole having a shape such as a number is made in the push button itself and a transparent resin is fit into the hole. As a result, the number or the like is easily visible when exposed to light from a rear side of the push button.
In addition, the demands for making electronic devices such as cellular phones thinner are strong. Therefore, a member for a push button switch mounted onto an electronic device such as a cellular phone is required to become thinner as well.
Patent Document 1: JP 2003-129248 A (for example, Scope of Claims)
Patent Document 2: KR 100454203 B (for example, Scope of Claims)
However, the aforementioned member for a push button switch has the following problems. In the case where a member for a push button switch having metallic appearance is manufactured by forming a plated layer on a surface of a resin molded portion, the plated layer is liable to be peeled off, which makes it difficult to be used for a long period of time. Further, providing a metallic appearance through plating process results in poor productivity, which has a bad influence on the environment. In addition, though taking on a metallic-like texture to a certain extent, the member for a push button switch subjected to the plating process can hardly be provided with a natural metallic appearance. Also in the case of a resin push button having a metallic appearance, because the resin is used as a material, some extent of thickness is required for ensuring intensity. The aforementioned matter is an obstacle to the attempt to make a member for a push button switch thinner.
On the other hand, in the case where a metal push button is attached to a surface of a flexible sheet such as a silicone rubber, because the metal push button is used, the problems described above hardly occur. However, the step of accurately positioning each metal push button on a keypad to be bonded thereto is extremely complicated. Further, the flexible sheet such as a silicone rubber exists in a gap between the metal push buttons, and thus there arises a problem in that a friction coefficient becomes relatively large in the gap portion, and the gap is easy to get dirty or stained.
The present invention has been made in view of the above problems, and an object thereof is to provide a member for a push button switch which has a natural metallic impression and upscale impression, enables a precise arrangement of the push buttons, can be made thinner, and is difficult to get stained.